Annealing furnace



July 30, 1935. A. N. o'rls Er AL ANNEALING FURNACE Filed March 21. 1954 2 Sheets-Sheet 1 Invenovs Albew N. Otis; James L. Mcovlond Then1 Attowneg.

WAHM'.

2 Sheets-Sheet 2 July 30, 1935. A, N. orls ET AL ANNEALING FURNACE Filed March 21, 1934 Patented Julyl 30, 1935 lP-A'rENT OFFICE ANNELING FURNACE Albert N. Otis and James L. McFarland, Schenectady, N. Y., assignors to General Electric Company, a corporation of New York Application March 21, 1934, Serial No. 716,629

21 Claims.

Our invention relates toannealing furnaces of 'the type which provides for the continuous movement of the material to be annealed through the furnace. It relates particularly to annealing furnaces adapted for use in annealing material in strip form, such for example as steel strip.

One object of our invention is the provision of an annealing furnace which in consideration of its output capacity .has relatively small cubical contents and requires relatively small floor space and head room. Another object of our invention is that the furnace shall provide for a maximum heat recovery from the material being annealed, hence reducing the heat requirements and giving to the furnace a high heat eficiency. A further object of our invention is the provision of an annealing furnace of the' continuous type wherein the material being annealed is supported Iand moved while heated to the proper temperature without danger of having the surface thereof scratched or otherwise damaged. A still further .object of our invention is the provision of means for regulating the passage of the material through the furnace.

Our invention will be better understood from the following description taken in connection with the accompanying drawings, and, its scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 is a vertical sectional view of an annealing furnace comprising an embodiment of our invention;` Fig. 2 is a similar vertical sectional view at right angles to that of Fig. 1; Fig. 3 is an enlarged detail view corresponding to Fig. 2 showing the upper portionrof the furnace; and Fig. 4 is a. circuit diagram of the drive and control apparatus of the furnace.

In Fig. 1 we have shown the furnace comprising an outer housing I which may be built up of 4o structural steel parts 2 to which are secured steel plates 3. The housing preferably is supported with its lower end in a pit 4 arranged below the level of the floor 5 thereby effecting economy in the necessary head room required. The housing which is provided with a lining 6 of heat insulating material forms three vertically aligned chambers, a lower heating chamber 1, an upper drum chamber l and an intermediate heat exchange chamber 9. 'I'hese chambers preferably 5o are maintained full of a suitable non-oxidizing gas such, for example, as hydrogen, or a mixture of hydrogen and nitrogen, the furnace being shown provided with the gas supply pipe I0 located near the top thereof and with the outlet openings II, of which one is located at the (Grasa-3) bottom of the heating chamber and the other nearv the 4roll 32. In accordance with the usual f practice the heating chamber I is provided with an additional lining' I2 of refractory ,material and on-the walls are located series of heating ele- 5 ments shown'at I3 infront of which are suitable guards l3'. These elements are preferably electric resistance elements and suitable temperature controlling devices, not shown, are employed for regulating the heating elements wherebythe desired temperature is maintained in the heating chamber. As shown in Fig. 2, the heating chamber is provided at one side with the door I4 whereby access may be had to this chamber forA the' installation and subsequent maintenance ofthe heating units, etc.

The drum'chamber 8 in the upper portion of the housing is likewise provided with doors I5,y one being shown in this case on each side of the chamber, in order to give access to the chamber, such for example, as when a new strip of material to be annealed is to be threaded through the furnace. Supported in the chamber 8 are the two hollow drums I6" and I1 by which the ma,-` terial to be annealed is suspended in a loop I8, which hangs with its two sides in close space relation and approximately parallel through the heat exchange chamber 9 and into the heating chamber 1. Both drums I6 and I'I are rotatably mounted on shafts which, as shown in Fig. 3, are non-rotatably supported by the brackets I9 secured to the outer face of the housing. The drums are each mounted on hollow trunnions encircling their respective shafts and passing through apertures in the opposite walls of the furnace. The trunnions are in turn mounted at their ends on their respective shafts by bearings 20 which as shown in Fig. 3 are mounted outside of the housing whereby they operate in a cooler atmosphere than if arranged within a drum chamber. The lower and smaller drum I'I is arranged to run freely on its shaft. The upper or larger drum I6 is arranged to be driven by the motor 22 through a suitable worm reduction gearing 23 andthe chain connection 24. By this means 5 drum I6 is rotated to feed the material to be annealed into the loop at the proper speed under the control of apparatus which will be described hereinafter. The material to be annealed is withdrawn by the drum I6 from the coil 26 through the rider 50 rolls 21 and under the roll 28. Obviously suitable protective means including a drop bar arranged to engage the material between the groups of rolls 21 may be provided if desired to stop motor 22 in case a free end of the material should pass the first group of rolls. From the drum I1' the material after annealing is withdrawn from the furnace by the reel 30, whichfor example is shown driven by the motor 3I, the material passing under the roll 32 and through the cooling chamber 33 in which the temperature of the material is reduced Yto such a point that oxidation 'will not occur when the material is exposed to the air. Where the strip enters and leaves the furnace it passes through the seals shown at 34 which, for example, may comprise thin steel plates covered with asbestos fabric. Between these seals and the drums I6 and I1 the strip is shown extending through a passage or chamber which connects at its upper end with the drum chamber 8.

At the opposite ends ofthe `heat exchange chamber 9 we have lshown seals for restricting the transfer of hot gas from the heating chamber into the heat exchange chamber and also from the latter chamber into the drum chamber. These seals are represented-as comprising the two outer vane-like members 35 which areY pivotally mounted in the small recesses 36 in the lining of the. housing and have operating handles 38 at the outside whereby they maybe turned upwardly so as to occupy the recesses. 'I'he'seals also comprise the central members 31 which are arranged so that they may be withdrawn bodily from the side of the furnace by the rings 39. The seals 35 and 31 are spaced from each other only sufficient to al-low the strip material to pass freely therebetween. 'Ihey are provided with rounded faces adjacent the strip and are' constructed or at least the adjacent faces thereof are constructed preferably of a suitable soft metal such as copperl so as to avoid any possible scratching of the strip material should it have a 4polished face and rub against one or more of the seals. With the members 35 turned up into the recesses and the members 31 withdrawn, a free path is provided for the threading of a strip of material to be annealed through the furnace.

For guiding the material laterally, we-have provided the two bars 40 through which are threaded the shafts 4I having righthand and lefthand threads. These shafts are connected at one side Vof the furnace by chain gearing-42 and at the other side of the furnace one of-the shafts is provided with the hand wheel 43, so that the bars may be separated or brought closer. together as may be required for different widths of strip which it may be required to anneal. The position of both bars 4I) may be simultaneously adjusted by turning the hand wheel.

In order to cause the material being annealed to cling without slippage to the drums I6 and I1, which slippage might produce objectionable scratches on the material, particularly in the case where the material being annealed is bright, we have provided both drums with magnetic means arranged therein. Such magnetic means comprise magnets represented at 44, the same being secured to the xecl shafts on which the drums rotate, and in positions opposite the upper portion of the surfaces of the drums ,which are engaged by the strip of material as it passes over the drums. Where magnets are employed within the drums the faces of the drums are constructed of non-magnetic material, such as copper, whereby the flux from the magnets may readily reach the material being annealed, such as sheet steel, to cause it to cling firmly to the faces of the drum.

For the regulation of the lspeed of motor 22 by which the'upper drum I6 is rotated we have proy vided -a control apparatus responsive to. the length of the loop I8.' 4AFor this purpose we vhave provided two aligning transverse openings in the Y lower portion of the furnace opposite the end of the loop I8. In a suitable housing arranged at" relay or that connectedwith the upper photoelectric device is arranged to close its contacts when light to its photoelectric device is unob- A structed by 'the 4loop I8, while the lower relay 50 or that one connected with the lower photoelectric device is arranged to close the circuit of its contacts when light to its photoelectric device is obstructed by the loop. Motor 22 which drives drum I6 is shown having its armature circuit energized from the source of current 52 through the switch 53. Its field winding 54 is also connected to the same source 52 through the rheostat 55. The position of the arm of this rheostat is moved by the motor 56 which is also connected to be supplied from the source 52 and is provided with the two reversely wound series eld windings 51 and 58. These windings are connected in circuit through the contacts of the relays 56 whereby the motor 56 is energized through one or the other of. the windings in accordance with the position of the end of the loop I8 of material to be annealed. In circuit with the motor 56 we have shown the switch 59 arranged to be intermittently closed and opened by the cam 60 which is driven at slow speed by the motor 6I whereby motor 56 is rendered operative at intervals and for only a portion of the total time.

It will be seen that with the above-described apparatus as long as the material to be annealed is being fed into the loop I8 at the same speed as that at which it is being withdrawn from the loop, the length of the loop will not change and the rheostat 55 will not change in value. Should the loop become too short, as would occur if the the field winding 51 which in turn will cause y motor 56 to run in such a direction as to shift the rheostat so as to weaken the eld produced by winding 54 of motor 22 thus increasing its speed. Conversely if the loop becomes too long the lower photoelectric device 48 will be shadowed by the loop and the lower relay 50 by being deenergized will close the circuit of motor 56 through field winding 58 causing motor 56 to run in the opposite direction and so changing rheostat that the eld produced by winding 54 is strengthened whereby the drum I6 is rotated at decreased speed.

The cooling chamber 33 in lwhich the strip is cooled below the point at which oxidation would occur were the strip to be exposed to the air is l temperature of the gas as it is drawn from theY chamber is reduced by the cooler 61. Cooling apparatus such as described above is disclosed and claimed in the copending application by Albert N. Otis, Serial No. 742,132 led Aug. 30, 1934, and assigned to the same assignee as the present application.

We have chosen the particular embodiment described above as illustrative of our invention and it will be apparent that various modifications may be made without departing from thespirit and scope of our invention which modifications we aim .to coverby the appended claims:

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An annealing furnace comprising a heating f chamber, means for supporting therein a loop of material to be annealed, a heat exchange chamber connecting with said heating chamber and means for feeding the material through the heat exchange chamber into the heating chamber and for withdrawing' the material through the heat exchange chamber from the heating chamber, the material approaching and leaving the heating paths in said heat. exchange chamber.

2. An annealing furnace comprising a heating chamber, means for suspending therein a loop of flexible material to be annealed, a heat exchange chamber having one end connecting with said heating chamber and means 'for feeding the material into the heating chamber and for withdrawing it therefrom, said material in approaching and leaving said heating chamber being.

passed through said heat exchange chamber in closely adjacent paths whereby a rapid exchange of heat may take place.

3. An annealing furnace comprising a heating chamber, a heat exchange chamber arranged thereover, means for suspending a loop of material to be annealed with its lower end portion in said heating chamber and with the opposite sides of another portion thereof adjacent to each other in said heat exchange chamber and means for feeding the material into one side of the loop and for withdrawing it from the other side thereof.

4. A n annealing furnace comprising a heating chamber, a heat exchange chamber arranged thereover, means arranged above said heat exchange chamber for suspending a loop of material to be annealed with its lower end in said heating chamber a'nd with the opposite sides of an intermediate portion of the loop adjacent to each other in said heat exchange chamber and means for feeding the material into one side of the loop and for withdrawing it from the other side thereof.

5. An annealing furnace comprising a heating chamber, a heat insulated heat exchange chamber arranged thereover, rotatable means forl suspending a loop of material to be annealed with its lower end portion in said heating chamber and with the opposite sides of another portion thereof in close heat exchange relation with each other in said heat exchange chamber and means for continuously feeding the material into one side of the loop and for withdrawing it from the other side thereof. f

6. An annealing furnace comprising an upper chamber, a lower heating chamber, an intermediate heat exchange chamber, rotatable means in said upper chamber for suspending a loop of material to be annealed with the lower end of the loop in said heating chamber and with both sides of an intermediate portion of the loop in said heat exchange chamber.

7. An annealing furnace comprising an upper relatively cool chamber, a lower heating chamber, an intermediate heat exchange chamber, drums in said upper chamber for suspending a loop of material to be annealed with the lower end of the loop in said heating chamber and with both sides of an intermediate portion of the loop in said heat exchange chamber, the relative position of said drums being such that the two sides of the loop in the heat exchange chamber are close to and in good heat exchange relation with each other.

8. An annealing furnace comprisinga heating chamber, means for suspending a loop of moving material to be annealed in said chamber, driving means for moving said material through said chamber and means responsive to the length of the loop for controllingsaid driving means to maintain the length of said loop at a predetermined value.

9. An annealing furnace comprising a heating chamber, a' heat exchange chamber arranged thereover, means for suspending a loop of material to be annealed with its lower end portion in said heating chamber and with the opposite sides of another portion thereof adjacent to each other in said heat exchange chamber, materialmoving means for feedingthe material into one side of the loop, material-.moving means for withdrawing the material from the other side of the" loop and means responsive to the length of the loop for controlling one o`f said material-moving means so as to maintain the length of said loop at a predetermined value.

10. An annealing furnace comprising a heating chamber, means for suspending a free loop of moving material to be annealed in said chamber, means for directing a light beam across said chamber, a photoelectric device arranged to receive said beam, the beam being arranged to be intercepted by the loop when the latter reaches a predetermined length and means responsive .to' said device for controlling the length of the loop;

1l. An annealing furnace comprising a heating chamber, a heat exchange chamber above the heating chamber, a drumfor suspending each side of a free loop of material to be annealed in said chambers, means for withdrawing the material from one side of the loop over one drum, means for .rotating the other drum to feed the material to the other side of the loop, means for directing alight beam across said chamber and positioned to be intercepted by the end of said loop, a photoelectric device arranged to receive said beam and means responsive to said device for regulating the speedof said other drum.

13. An annealing furnace comprising a heating furnace having walls of heat refractory material and having heating units arranged on the walls thereof, a heat exchange chamber arranged above theA heating chamber and having walls of heat insulating material, a drum chamber arranged above the heat exchange chamber, ad-

'justable seals between 'said chambers, drums in said drum chamber for supporting a loop ofmaterial to be annealed in the heating and heat exchange chambers, said drums being so arranged that the two sides of said loop hang close space relation with 'each other.

14. A'n 'annealing furnace comprising a vertical housing havinga lining of heat insulating' material, the lower portion of said housing comprising a heating chamber having heating means therein, an intermediate portion of the housing comprising a heat exchange chamber and the upper portion of said housing comprising a rela- Y tively cool drum chamber, seals operable from the exterior of the housing at each end of the heat exchange chamber, drums in the ldrum chamber arranged 'to suspend the two sides of a loop of material 'to be annealed in the heat exchange and theheating chambers, means for withdrawing the material from one side of the loop and means for rotatingone of the drums tosupply material to the other side of the loop.

15. An annealing furnace having a hollow drum therein for supporting the material to be annealedV and provided with a hollow shaft at A each end thereof, a fixed shaft extending through said drum and hollow shaft and a magnet secured to the fixed shaft within the 16. An annealing furnace having a hollow drum therein for supporting the material to be annealed and provided with a hollow shaft at each end-thereof extending through the walls of the furnace, bearings for said hollow shaft at the exterior of' said furnace, a fixed shaft extending through the drum and hollow shaft and a magnet within said drum secured to the fixed shaft.

1 7. In a furnace having a chamber provided with an opening therein through which material is adapted to pass simultaneously into and out of4 the chamber in adjacent paths, sealing 'means for said opening comprising members aroppdsite sides with said material and ainovable member at each side of said opening arranged to cooperate with said material.

19. In a furnace having a chamber providedl with an opening therein through which material is adapted to pass simultaneously into and out of the chamber in adjacent paths, sealing means for said opening comprising a plurality of outer pivotally mounted`mexnbers and an intervmediate member, means for moving the outer 4communicating therewith, drums in said drum chamber from-which strip material to be annealed is adapted to be suspended in a loop in the heating and heat exchange chambers. seals between the heating and heat exchange chambers and between the heat exchange chamber and the drum chamber, means for driving one of said drums,` means for controlling said driving means including aphotoelectric device arranged to respond to the length of the loop and means for supplying a non-oxidizing gas to said furnace.

21. An annealing furnace comprising a heating chamber having heating elements therein, a heat exchange chamber arranged thereover and in communication therewith. seals between said chambers, a drum chamber over said heat exchange chamber, seals therebetween, a plurality of drums in said drum chamber from which a continuously moving strip of material is adapted to be suspended in a loop Ain said heat exchange and heating chambers, a motor mounted on the furnace for moving one of said drums, magnets in said drums for causing the material to cling thereto, said furnace having an provided with seals through which the strip is adapted to enter and leave, photoelectric devices arranged to be affected by the length of said loop, control apparatus for said motor responsive to said devices and means for admitting a nonoxidizing gasto the drum chamber of said furnace.

ALBERT N. O'I'IS. JAMES L. MCFARLAND. 

